The greenhouse effect by CO2 (carbon dioxide) has been pointed out as one of the causes of the global warming, and there is an urgent need to take measures against it for protecting the global environment on a global scale. The generation source of CO2 ranges over all human activities that burn fossil fuel, and thus demands for emission limitation on CO2 are further increasing. Along with this trend, targeting for power generating facilities such as a thermal power plant that uses a large amount of fossil fuel, a method of reducing and recovering CO2 in flue gas by bringing flue gas from a boiler into contact with an amine absorbent such as an amine compound solution has been intensively studied.
As a CO2 recovery unit that recovers CO2 from flue gas from a boiler or the like by using an absorbent, there has been known a CO2 recovery unit that reduces CO2 in flue gas by bringing flue gas into contact with a CO2 absorbent in an absorber, heats the absorbent that has absorbed CO2 in a regenerator so as to emit CO2 and to regenerate the absorbent, and then returns the absorbent to the absorber and reuses the absorbent (see, for example, Patent Literature 1).
To separate and recover CO2 in the regenerator, the absorbent needs to be heated in a reboiler, and thus steam of a predetermined pressure for heating needs to be supplied. Conventionally, it has been proposed to regenerate the steam by using a part of steam generated in a combustion facility such as a boiler in a power plant (see, for example, Patent Literature 2).
Steam supplied to the regenerator becomes condensed water after heating the absorbent that has absorbed CO2, and is returned to a combustion facility and heated again.